WASHINGTON — A $150 billion windfall Iran would get after a deal to curb its nuclear program is raising new alarms in Congress that it will use the money to boost terrorist funding across the Middle East.

Top Republican and Democratic senators propose legislation that would impose penalties on Iran if it used the money to spread mayhem.

James Clapper, Obama's director of national intelligence, calls Iran the world's "foremost state sponsor of terrorism," citing Iran's support for Hezbollah in Lebanon, Bashar Assad's regime in Syria and Houthi insurgents in Yemen.

Yet the Obama administration argues that a nuclear deal with world powers and increased revenue would reduce Iran's isolation, potentially leading to a more constructive Iranian foreign policy.

State Department spokesman John Kirby said Iran's support of terrorism "remains a concern," but U.S. policy has been that the nuclear talks will impact only sanctions targeting Iran's nuclear program. Terrorism-related sanctions will remain unless Iran ends its support for terrorism, Kirby said.

There's hope that success on the nuclear deal "could lead to other openings with Iran on other issues that could possibly have a positive benefit in terms of their behavior and conduct on a whole range of other security matters in the region," Kirby said.

The United States and other world powers are trying to clinch a deal with Iran by Tuesday. The pace for lifting sanctions has been one of the main sticking points. Secretary of State John Kerry has said sanctions would be lifted as Iran implements terms of the deal, while Iran wants all sanctions lifted immediately.

Diplomats told the Associated Press on Saturday that a tentative agreement on sanctions relief had been reached, but senior officials including Kerry and Iranian Foreign Minister Javad Zarif still needed to sign off on the package, which outlines what specific U.S. and international sanctions would be lifted and when. The diplomats weren't authorized to speak publicly on this past week's confidential negotiations in Vienna.

Zarif has complained that world powers seek to prolong the lifting of sanctions, betraying a lack of trust. "Western countries need to make their political decision as to whether they are after an agreement or seek to continue pressures," Zarif said Friday, according to Iran's Tasnim News Agency.

Yukiya Amano, chief of the U.N. nuclear watchdog, the International Atomic Energy Agency, said Saturday in Vienna that Iran could resolve his organization's questions about possible weapons work by the end of the year. "I think we can issue a report by the end of the year on the ... clarification of the issues related to possible military dimensions" of Iran's nuclear program, Amano said after returning from Tehran, according to Radio Free Europe.

Amano traveled to Iran this week to talk to President Hassan Rouhani about his nation's past nuclear activities, suspected weapons work and gaining access to Iran's civilian and military nuclear facilities in the future.

The White House has estimated the value of Iran's foreign accounts frozen by nuclear sanctions at $150 billion. The lifting of other sanctions would allow Iran to boost its oil production from 2.9 million barrels a day to 4.2 million barrels a day by 2020, according to a report by Washington-based energy analyst Sara Vakhshouri of SVB Energy International. Iran's oil production is worth about $60 billion a year on the world market. Oil prices are likely to fall in reaction to Iran's new oil output, Vakhshouri said.

Senate Majority Leader Mitch McConnell, R-Ky., urged Obama to rethink the negotiations, arguing that Iran is expanding its ballistic missile program and supporting "terrorist proxies" that pose a threat to the United States and its allies. Giving Iran access to more cash "would only make those problems worse," McConnell said.

Sens. Bob Menendez, D-N.J., and Mark Kirk, R-Ill., have proposed legislation that would require the United States to confirm that Iranian-backed terrorist organizations "aren't the beneficiaries of newly accessed Iranian funds."

In addition to freeing Iran's cash, primarily in Japanese and South Korean bank accounts since 2012, an accord would allow Iran to freely sell its oil on the world market and attract foreign investment to boost its production capacity.

Karim Sadjadpour, an Iran analyst at the Carnegie Endowment for International Peace, said a nuclear deal is unlikely to change Iran's policy of challenging U.S. dominance in the Middle East, its refusal to accept the state of Israel and its rivalry with U.S.-ally Saudi Arabia.

"If they had more money, they'll continue to spend it in the same way," he said.

Alireza Nader of the RAND Corp. said Iran's dilapidated public infrastructure and failing health, welfare and education sectors create a public demand for better services and a healthier economy as soon as sanctions are lifted.

Iran's Islamic Revolutionary Guards, who fund military operations in part through financial enterprises they control, "will benefit from sanctions if there's a nuclear deal," Nader said. "But I think most of it will be consumed internally."

"They've been unable to make significant investments for 10 years," Batmanghelidj said. "This is a pragmatic government, and it would be madness to bring all that money back and spend it on a militia fighting in Syria."